The invention concerns genomic and cDNA sequences of the human TBC-1 gene. The invention also concerns polypeptides encoded by the TBC-1 gene. The invention also deals with antibodies directed specifically against such polypeptides that are useful as diagnostic reagents. The invention further encompasses biallelic markers of the TBC-1 gene useful in genetic analysis.
The incidence of prostate cancer has dramatically increased over the last decades. It averages 30-50/100,000 males in Western European countries as well as within the US White male population. In these countries, it has recently become the most commonly diagnosed malignancy, being one of every four cancers diagnosed in American males. Prostate cancer""s incidence is very much population specific, since it varies from 2/100,000 in China, to over 80/100,000 among African-American males.
In France, the incidence of prostate cancer is 35/100,000 males and it is increasing by 10/100,000 per decade. Mortality due to prostate cancer is also growing accordingly. It is the second cause of cancer death among French males, and the first one among French males aged over 70. This makes prostate cancer a serious burden in terms of public health.
Prostate cancer is a latent disease. Many men carry prostate cancer cells without overt signs of disease. Autopsies of individuals dying of other causes show prostate cancer cells in 30% of men at age 50 and in 60% of men at age 80. Furthermore, prostate cancer can take up to 10 years to kill a patient after the initial diagnosis.
The progression of the disease usually goes from a well-defined mass within the prostate to a breakdown and invasion of the lateral margins of the prostate, followed by metastasis to regional lymph nodes, and metastasis to the bone marrow. Cancer metastasis to bone is common and often associated with uncontrollable pain.
Unfortunately, in 80% of cases, diagnosis of prostate cancer is established when the disease has already metastasized to the bones. Of special interest is the observation that prostate cancers frequently grow more rapidly in sites of metastasis than within the prostate itself.
Early-stage diagnosis of prostate cancer mainly relies today on Prostate Specific Antigen (PSA) dosage, and allows the detection of prostate cancer seven years before clinical symptoms become apparent. The effectiveness of PSA dosage diagnosis is however limited, due to its inability to discriminate between malignant and non-malignant affections of the organ and because not all prostate cancers give rise to an elevated serum PSA concentration. Furthermore, PSA dosage and other currently available approaches such as physical examination, tissue biopsy and bone scans are of limited value in predicting disease progression.
Therefore, there is a strong need for a reliable diagnostic procedure which would enable a more systematic early-stage prostate cancer prognosis.
Although an early-stage prostate cancer prognosis is important, the possibility of measuring the period of time during which treatment can be deferred is also interesting as currently available medicaments are expensive and generate important adverse effects. However, the aggressiveness of prostate tumors varies widely. Some tumors are relatively aggressive, doubling every six months whereas others are slow-growing, doubling once every five years. In fact, the majority of prostate cancers grows relatively slowly and never becomes clinically manifest. Very often, affected patients are among the elderly and die from another disease before prostate cancer actually develops. Thus, a significant question in treating prostate carcinoma is how to discriminate between tumors that will progress and those that will not progress during the expected lifetime of the patient.
Hence, there is also a strong need for detection means which may be used to evaluate the aggressiveness or the development potential of prostate cancer tumors once diagnosed.
Furthermore, at the present time, there is no means to predict prostate cancer susceptibility. It would also be very beneficial to detect individual susceptibility to prostate cancer. This could allow preventive treatment and a careful follow up of the development of the tumor.
A further consequence of the slow growth rate of prostate cancer is that few cancer cells are actively dividing at any one time, rendering prostate cancer generally resistant to radiation and chemotherapy. Surgery is the mainstay of treatment but it is largely ineffective and removes the ejaculatory ducts, resulting in impotence. Oral oestrogens and luteinizing releasing hormone analogs are also used for treatment of prostate cancer. These hormonal treatments provide marked improvement for many patients, but they only provide temporary relief. Indeed, most of these cancers soon relapse with the development of hormone-resistant tumor cells and the oestrogen treatment can lead to serious cardiovascular complications. Consequently, there is a strong need for preventive and curative treatment of prostate cancer.
Efficacy/tolerance prognosis could be precious in prostate cancer therapy. Indeed, hormonal therapy, the main treatment currently available, presents important side effects. The use of chemotherapy is limited because of the small number of patients with chemosensitive tumors. Furthermore the age profile of the prostate cancer patient and intolerance to chemotherapy make the systematic use of this treatment very difficult.
Therefore, a valuable assessment of the eventual efficacy of a medicament to be administered to a prostate cancer patent as well as the patent""s eventual tolerance to it may permit to enhance the benefit/risk ratio of prostate cancer treatment.
It is known today that there is a familial risk of prostate cancer. Clinical studies in the 1950s had already demonstrated a familial aggregation in prostate cancer. Control-case clinical studies have been conducted more recently to attempt to evaluate the incidence of the genetic risk factors in the disease. Thus Steinberg et al., 1990, and McWhorter et al., 1992 confirm that the risk of prostate cancer is increased in subjects having one or more relatives already affected by the disease and when forms of early diagnosis in the relatives exist.
It is now well established that cancer is a disease caused by the deregulation of the expression of certain genes. In fact, the development of a tumor necessitates an important succession of steps. Each of these steps comprises the deregulation of an important gene intervening in the normal metabolism of the cell and the emergence of an abnormal cellular sub-clone which overwhelms the other cell types because of a proliferative advantage. The genetic origin of this concept has found confirmation in the isolation and the characterization of genes which could be responsible. These genes, commonly called xe2x80x9ccancer genesxe2x80x9d, have an important role in the normal metabolism of the cell and are capable of intervening in carcinogenesis following a change.
Recent studies have identified three groups of genes which are frequently mutated in cancer. The first group of genes, called oncogenes, are genes whose products activate cell proliferation. The normal non-mutant versions are called protooncogenes. The mutated forms are excessively or inappropriately active in promoting cell proliferation, and act in the cell in a dominant way in that a single mutant allele is enough to affect the cell phenotype. Activated oncogenes are rarely transmitted as germline mutations since they may probably be lethal when expressed in all the cells. Therefore oncogenes can only be investigated in tumor tissues.
The second group of genes which are frequently mutated in cancer, called tumor suppressor genes, are genes whose products inhibit cell growth. Mutant versions in cancer cells have lost their normal function, and act in the cell in a recessive way in that both copies of the gene must be inactivated in order to change the cell phenotype. Most importantly, the tumor phenotype can be rescued by the wild type allele, as shown by cell fusion experiments first described by Harris and colleagues (1969). Germline mutations of tumor suppressor genes may be transmitted and thus studied in both constitutional and tumor DNA from familial or sporadic cases. The current family of tumor suppressors includes DNA-binding transcription factors (i.e., p53, WT1), transcription regulators (i.e., RB, APC, probably BRCA1), protein kinase inhibitors (i.e., p16), among others (for review, see Haber D and Harlow E, 1997).
The third group of genes which are frequently mutated in cancer, called mutator genes, are responsible for maintaining genome integrity and/or low mutation rates. Loss of function of both alleles increases cell mutation rates, and as a consequence, proto-oncogenes and tumor suppressor genes may be mutated. Mutator genes can also be classified as tumor suppressor genes, except for the fact that tumorigenesis caused by this class of genes cannot be suppressed simply by restoration of a wild-type allele, as described above. Genes whose inactivation may lead to a mutator phenotype include mismatch repair genes (i.e., MLH1, MSH2), DNA helicases (i.e., BLM, WRN) or other genes involved in DNA repair and genomic stability (i.e., p53, possibly BRCA1 and BRCA2) (For review see Haber D and Harlow E, 1997; Fishel R and Wilson T. 1997; Ellis N A, 1997).
There is growing evidence that a critical event in the progression of a tumor cell from a non-metastatic to metastatic phenotype is the loss of function of metastasis-suppressor genes. These genes specifically suppress the ability of a cell to metastasize. Work from several groups has demonstrated that human chromosomes 8, 10, 11 and 17 encode prostate cancer metastasis suppressor activities. However, other human chromosomes such as chromosomes 1, 7, 13, 16, and 18 may also be associated to prostate cancer.
It thus remains to localize and to identify the genes specifically involved in the development and the progression of prostate cancers starting from the genetic analysis of the hereditary and the non-hereditary forms and to define their clinical implications in terns of prognosis and therapeutic innovations.
The present invention pertains to nucleic acid molecules comprising the genomic sequence of a novel human gene which encodes a TBC-1 protein. The TBC-1 genomic sequences comprise regulatory sequence located upstream (5xe2x80x2-end) and downstream (3xe2x80x2-end) of the transcribed portion of said gene, these regulatory sequences being also part of the invention. The human TBC-1 genomic sequence is included in a previously unknown candidate region of prostate cancer located on chromosome 4.
The invention also deals with the two complete cDNA sequences encoding the TBC-1 protein, as well as with the corresponding translation product.
Oligonucleotide probes or primers hybridizing specifically with a TBC-1 genomic or cDNA sequence are also part of the present invention, as well as DNA amplification and detection methods using said primers and probes.
A further object of the invention consists of recombinant vectors comprising any of the nucleic acid sequences described above, and in particular of recombinant vectors comprising a TBC-1 regulatory sequence or a sequence encoding a TBC-1 protein, as well as of cell hosts and transgenic non human animals comprising said nucleic acid sequences or recombinant vectors.
The invention also concerns a TBC-1-related biallelic marker and the use thereof.
Finally, the invention is directed to methods for the screening of substances or molecules that inhibit the expression of TBC-1, as well as with methods for the screening of substances or molecules that interact with a TBC-1 polypeptide.